The factors that govern airflow into the respiratory tract

1. SUBMITTED BY: SUMI VARGHESE
ROLL NO.: 161126002
Seminar 1:
MECHANICS OF
VENTILATION

2.  Pressure Differences During Breathing
 Forces Opposing Inflation Of The Lung
i. Elastic opposition
ii. Frictional opposition
 Mechanics Of Exhalation
 Work Of Breathing
 Distribution Of Ventilation
CONTENTS

3.  Transrespiratory
pressure (PTR)
 Transairway
pressure(PAW)
 Transalveolar
pressure(PTA)
 Trans-chest wall
pressure(PTCW)
 Transpulmonary
pressure(PTP)
PRESSURE DIFFERENCES DURING
BREATHING

4. Airway, Alveolar And Intrathoracic Pressure,
Volume And Flow During Spontaneous Ventilation

5. Airway, Alveolar And Intrathoracic Pressure,
Volume And Flow During Negative Pressure
Mechanical Ventilation

6. Airway, Alveolar And Intrathoracic Pressure,
Volume And Flow During Positive Pressure
Mechanical Ventilation

7. Forces Opposing Lung Inflation
ELASTIC FORCES FRICTIONAL FORCES

8.  Elastic properties of the lungs:
1. Elastic force of the lung tissue
2. Surface tension at the air-liquid interface in
the alveoli
 Elastic properties of chest wall
 Total elastance
ERS = EL + ECW
*EL – lung/pulmonary elastance
*ECW- chest wall elastance
ELASTIC OPPOSITION TO
VENTILATION

9.  Lung compliance
 Compliance
1/Elastance= ∆V / ∆P
 Static compliance
 Dynamic compliance
 Chest wall compliance
 Interaction with chest
and chest wall

10.  Tissue viscous
resistance(20%)
 Airway
resistance(80%)
- Factors affecting
airway resistance
- Distribution of airway
resistance
FRICTIONAL OPPOSITION TO
VENTILATION
DISTRIBUTION OF AIRWAY
RESISTANCE
Location
•Nose, mouth,
upper airway
•Trachea and
bronchi
•Small airways
Total resistance
(%)
•50
•30
•20

11.  Normal quiet breathing
- Transmural pressure
 Forced exhalation
- Transmural pressure
 Equal Pressure Point
(EPP)
 Dynamic compression
of the airways
MECHANICS OF EXHALATION

12. Mechanical
work
Metabolic work
WORK OF BREATHING (WOB)

14.  Metabolic work
- ⩒O2
- Transdiaphragmatic
pressure(Pdi)
- SvO2
- O2 cost of breathing in
pulmonary diseases
WORK OF BREATHING
(WOB)

15.  Gravity
 ⩒/Q
1. Regional factors
- Differences in thoracic
expansion
- Transpulmonary
pressure gradients
2. Local factors
- Time constants
- Frequency dependence
of compliance
DISTRIBUTION OF VENTILATION